This invention relates to a material screening apparatus. More particularly, it relates to a barrel screen apparatus.
Screens are utilized for sorting material by size in various industries including construction, waste disposal, landscaping, and building demolition. Some such screens are substantially planar and screen by oscillating or shaking. Conventional trommel or barrel screens are cylindrical in shape, elongate, open at both ends and rotate. They are operated tilted at an angle from horizontal. The material to be processed is dumped into the higher end and the rotation causes the material to tumble to the lower end with screened or sifted material falling down through the screen and the balance of the material discharged out the lower open end. The screened material either accumulates on the ground below the screen or on a conveyor is positioned to catch the material and convey it out from underneath the apparatus. Trommel screens typically have an axial length of several diameters and thus a conveyor ideally would run lengthwise in order to take advantage of the screening action of the full length of the screen. With a lengthwise orientation of the conveyor, the conveyor must extend outwardly from the front or the rear of the apparatus. In that the front and the rear also are where the material enters the apparatus and exits the apparatus, a material handling problem exists.
One way this problem has been resolved is by allowing sufficient clearance between the rotating trommel screen and the ground and allowing the screened material to buildup on the ground where it is then removed by way of a front-end loader or similar device. This design requires that the entire apparatus be elevated which may be impractical or inconvenient in many situations and also raises the open receiving end making input of material more difficult.
A conveyor may be placed in position at a perpendicular angle extending out from under the trommel or barrel screen, however, this typically would only accept a portion of the material screened, creating the need for additional backup removal of the screened material that does not fall directly onto the conveyor.
An additional consideration in the efficient operation of barrel or trommel screen apparatus is that the feed to the receiving end of the trommel has to be regulated to avoid overloading the apparatus. Direct dumping into the receiving end by a front end loader or similar equipment will often overload the apparatus. A typical means of regulating the input is by way of a conveyor belt, where material is first dumped on a conveyor belt and is then conveyed into the open receiving end of the apparatus. This has a disadvantage in that it requires ancillary equipment and/or extends the required space for the operation.
A conveyor on prior art equipment may be self-contained on the same piece of equipment as the rotating trommel screen with a feed hopper at the distal end of the conveyor. This type of equipment has the disadvantage of greatly extended length, a more limited adjustment capability regarding the tilt from horizontal, and presents maintenance problems with the belt such as excessive wear and puncturing of the conveyor belt by the handling of the unscreened material.